Method and apparatus for loss of control inhibitor systems

ABSTRACT

Active and adaptive systems and methods to prevent loss of control incidents by providing tactile feedback to a vehicle operator are disclosed. According to the present invention, an operator gives a control input to an inceptor. An inceptor sensor measures an inceptor input value of the control input. The inceptor input is used as an input to a Steady-State Inceptor Input/Effector Output Model that models the vehicle control system design. A desired effector output from the inceptor input is generated from the model. The desired effector output is compared to an actual effector output to get a distortion metric. A feedback force is generated as a function of the distortion metric. The feedback force is used as an input to a feedback force generator which generates a loss of control inhibitor system (LOCIS) force back to the inceptor. The LOCIS force is felt by the operator through the inceptor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 60/515,215 filed Oct. 28, 2003, which is herebyincorporated by reference in its entirety.

ORIGIN OF THE INVENTION

The invention described herein was made by an employee of the UnitedStates Government and may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalty thereon or therefor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to man-machine compatibility with respectto closed-loop control of vehicles. Specifically, the present inventionrelates to tactile feedback systems. More specifically, the presentinvention relates to an improved and intuitive tactile feedback to thevehicle operator on the status of the vehicle's controls that countersthe current trend of utilizing control-by-wire and/or power controlsthat greatly reduce the operator's “feel” for the limitations imposed onthe control system by failures, configuration idiosyncrasies, seldomencountered and unanticipated operating conditions, and designlimitations that can result in catastrophic loss of vehicle control.

2. Description of the Related Art

Many vehicle control systems use hydraulic, mechanical, or electricalpower to augment the operator's control forces to reduce the operator'sworkload for maneuvering the vehicle. But the more work done by thepower system, the less tactile information is being transmitted backthrough the inceptor to the operator on the status of the controlsystem. For example, the operator will not detect the increase incontrol forces on a system in need of lubrication as readily because thepower system is providing much of the additional force required. Forlarge vehicles, such as commercial aircraft, there is further masking ofinformation by the system compliance, the stretching of cables, thebending of the mounting brackets and push rods, and the over-travelsprings on the actuator servo valves.

The latest advance in vehicle control technology to be widelyimplemented is the control-by-wire, which replaces the forcetransmitting mechanical linkage between the inceptor and the effectorwith a wire transmitting the inceptor generated electric signalcommanding the effectors to action. A multitude of benefits areattributed to the adoption of control-by-wire technology, but thecompromise was the acceptance that tactile feel for the status of theflight control system were either not needed, or could be providedthrough alternate sensory channels. One of the unanticipatedconsequences of replacing the mechanical linkage with wire, was theresulting incidences of operators, when unexpectedly encountering a lifethreatening situation, responding by moving their inceptors at such arate that the effectors could not keep up, markedly increasing the phasedelay between the inceptor input and the associated effector output.Phase delay is a key factor in the experiencing of loss of controlassociated with the aircraft-pilot or operator-vehicle couplingphenomena.

Loss of control from aircraft-pilot coupling is the result of the pilottrying aggressively to help the aircraft either recover from an upset,or to acquire a new flight path because of an impending threat on theoriginal course. Under such circumstances, the pilot will choose to actlike an additional stability augmentation system in order to moreresponsively acquire the desired flight path, and quickly dampen anyovershoots resulting from the recovery maneuver. The consequences of thephase delay are that while the pilot's inceptor inputs are trying toenhance the stability, the resulting effector output may be doing justthe opposite because of the phase delay.

The invention fills the void created by the adoption of control-by-wiretechnology in tactile feedback through the inceptor to the vehicleoperator on the status of the critical functions of the vehicle controlsystem.

“Loss of Control” was the single largest fatal accident category for theworldwide commercial jet fleet from 1994 through 2003, and hasconsistently been either the first or second largest fatal accidentcategory since the beginning of accident data collection. Specificfactors that cause loss of control are many and varied, but a commonindicator for several recent aircraft accidents has been the lack ofawareness by the pilot of anomalous behavior of the flight controlsystem, caused by a control surface not following the pilot's commandsto the level of accuracy needed to maintain control of the aircraft.

With the degree of technical sophistication involved in assuring thattoday's aircraft are easily controllable, with redundancy providingfail-safe operations even after one or two failures of key components,there continues to be room for improvement. Recent advances in flightcontrol designs, such as fly-by-wire, have eliminated the pilot'stactile feel for a jammed or frozen control surface, or for hitting thecontrol surface deflection stop. Generally, there is little or norestraining force on the cockpit inceptors to alert the pilot forexceeding the control surface rate limits. Such tactile feedback, whichwas an implicit pilot cue in early aircraft, is substantially erodedwith the introduction of the fully powered hydro-mechanical controlsystems, and completely eliminated with the introduction of fly-by-wirecontrol systems.

Other vehicle types are adapting control systems that utilizecontrol-by-wire technology. The control-by-wire (CBW) control systems,when used as part of the vehicle's primary maneuver controls, aresubject to the same challenges that have been experienced in airvehicles. For example, the loss of tactile feedback to the operator ondeteriorating conditions of the control system and the anticipatedvehicle response, which can lead to loss of control unless appropriatelycompensated for by the operator.

An approach to addressing the problems noted above is to provide thevehicle operator with tactile feedback on deteriorating conditions withthe vehicle controls. Specifically, one way this can be accomplished isby providing increasing resistance to the inceptor proportional to theseverity of the deterioration, the vehicle operator will initially bealerted by the increased resistance felt during control application,with the resistance ultimately increasing to thereby maintain safecontrol of the vehicle.

There have been attempts to address the problems noted above. Forexample, U.S. Pat. No. 6,339,419, issued to Jolly et al., refers to amagnetically controllable system. In Jolly '419, a haptic.interfacesystem using force feedback and a magnetically-controllable device thatprovides resistance forces opposing joystick movement is disclosed. Thesystem includes a computer system that runs a program similar to acomputer game that can use a joystick which is similar to that used inan aircraft. The joystick is in contact with a pilot or an operator andthe haptic interface device which is in contact with the controllerprovides resistance to the operator's motion. The computer systemprovides a variable output signal corresponding to a feedback force andthe magnetically controllable device varies the feedback force based onthe output signal. The feedback force is varied by changing the densityof the magnetically controlled fluid in response to the output signal.Similarly, U.S. Pat. No. 6,373,465, issued to Jolly et al., discloses amagnetically controllable device adapted for use in a feedback computersystem to provide force feedback sensations to the system's operator.The system in Jolly '465 includes a computer system that runs a programwhich controls a haptic interface device, similar to a joystick in anaircraft.

U.S. Pat. No. 6,283,859, issued to Carlson et al., discloses a feedbacksystem using a magnetically controllable haptic interface system whereina magnetically controllable fluid is employed in the device. Carlson'859 is directed to providing computer game operators with “feelsensations” so they can get a realistic simulation of the computerizedgame. According to Carlson, a variable resistance force in proportion tothe strength of an applied magnetic field is provided.

U.S. Pat. No. 5,062,594, issued to Repperger, discloses a flight controlsystem with tactile feedback. In Repperger '594, there is a roll systemwhich has visual feedback and includes a feedback system which providesfeel derived from signal sources. Repperger '594 uses an algorithm whichis characterized mathematically. The control system in Repperger '594 isa passive control system, wherein feedback forces are based on the pilotinput to the flight control system.

Lastly, U.S. Pat. No. 4,599,070, issued to Hladky et al., discloses amethod and system apparatus for simulating a control system, such as anaircraft control system. According to Hladky '070, a moveable control issimulated in which force and movement parameters of the control can bevaried in accordance with, simulated operation of the system. Feedbackfeel is accomplished through the use of levers having an adjustablefulcrum. The control system in Hladky '070 is a programmed passivesystem, wherein forces are simulated based on the programmed set ofsimulated conditions.

There remains a need for a tactile feedback system that can alert theoperator, through tactile feedback generated by increasing the frictionforce on the inceptor as a function of the severity of potential loss ofcontrol conditions. Furthermore, there remains a need for a tactilefeedback system that can produce a restraining force to counter operatorvehicle coupling loss of control conditions. Thus, it would beadvantageous to provide an improved tactile feedback system that canalert the operator, through tactile feedback generated by increasing thefriction force on the inceptor as a function of the severity ofpotential loss of control conditions. It would also be advantageous toprovide an improved tactile feedback system that can produce a retainingforce to counter operator vehicle coupling loss of control conditions.

In view of the deficiencies described above, it is an object of thepresent invention to provide an improved tactile feedback system thatcan alert the operator, through tactile feedback generated by increasingthe friction force on the inceptor as a function of the severity ofpotential loss of control condition. It is a further objective toprovide an improved tactile feedback system that can produce a retainingforce to counter operator vehicle coupling loss of control conditions.

It is a further objective of the present invention to alert theoperator, through tactile feedback generated by increasing the frictionforce on the inceptor as a function of the severity of the condition,where the loss of control conditions can include, but are not limitedto, displacement and rate limiting of the effector; misrigging ormisalignment of the inceptor to effector relationship; motion limitingincrease in resistance of the effector, which is not reflected at theinceptor; a deterioration of control/response harmony as a result ofactuation of a safety-enhancing/envelope-limiting system; adeterioration of control/response harmony as a result of unanticipateddegradation of the control system under unexpected operating conditions;aggressive inceptor inputs by the operator which are outside thedesign-operating envelope of the control system and would result in apotential loss of control; inceptor inputs by the operator which areoutside the safe-operating envelope of the control system as a result ofa failure/degradation in power system driving, the effector and wouldresult in a potential loss of control. The criticality of theseconditions is appropriately reflected by a difference between ananticipated effector response to an inceptor input and the actualeffector response.

The present invention includes active and adaptive systems and methodsto prevent loss of control accidents and incidents by providing advisoryinformation via tactile feedback to a vehicle operator on the status ofthe vehicle's control functions for a broad range of debilitatingconditions.

According to the present invention, an operator gives a control input toan inceptor. An inceptor sensor measures a value, inceptor input, of thecontrol input. The inceptor input is used as an input to a Steady-StateInceptor Input/Effector Output Model that models the vehicle controlsystem design.

The model is used to generate a desired effector output from theinceptor input. The desired effector output is compared to an actualeffector output. Actual effector output is measured by an effectorsensor.

A distortion metric is generated from the comparison of the desiredeffector output to the actual effector output. A feedback force isdetermined from an evaluation of the distortion metric. Generally, thefeedback force is a function of the distortion metric. The feedbackforce is used as an input to a feedback force generator which generatesa loss of control inhibitor system (LOCIS) force back to the inceptor.The LOCIS force is felt by the operator through the inceptor.

Other features and advantages of the invention will be apparent from thefollowing detailed description taken in conjunction with the followingfigures, wherein like reference numerals represent like features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a loss of control inhibitor system according to the presentinvention in block diagram form.

FIG. 2 shows a Steady-State Inceptor Input/Effector Output Modelaccording to the present invention.

FIG. 3 shows inceptor/effector responses with and without a loss ofcontrol inhibitor system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible of embodiments in many differentforms, there are shown in the drawings and will herein be described indetail, preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiments illustrated.

The present invention includes active and adaptive systems and methodsto prevent loss of control accidents and incidents by providing advisoryinformation via tactile feedback to a vehicle operator on the status ofthe vehicle's control functions for a broad range of debilitatingconditions. Vehicles incorporating control-by-wire, that is, theinceptor's input command signal to the effector is sent by other thanmechanical means, are generally void of any tactile feedback through theinceptor regarding control anomalies, and therefore have the most togain from application of the invention.

FIG. 1 shows a loss of control inhibitor system according to the presentinvention in block diagram form. In the system, an operator 110 gives acontrol input 120 to an inceptor 130. An inceptor sensor 140 measures avalue, inceptor input, δ_(I), 200, of the control input 120. In variouspreferred embodiments, the inceptor sensor 140 measures inceptor 130position and/or inceptor 130 rate. The inceptor input 200 is used as aninput to a Steady-State Inceptor Input/Effector Output Model (the Model)150, that models the vehicle control system design.

The Model 150 is defined by the vehicle control system team. Typically,the Model 150 is based on prior design experience, man-machine studies,simulations, and prototype tests. FIG. 2 shows a Steady-State InceptorInput/Effector Output Model according to the present invention. TheModel 150, shown in FIG. 2, shows inceptor input, δ_(I), 200 on thehorizontal axis 210 and effector output, δ_(O), 220 on the vertical axis230. An effector to inceptor design gain, K_(δO/δI), 240 can be definedas change in effector output 220 divided by the change in inceptor input210, or dδ_(O)/dδ_(I). A tolerance band, Δδ_(O), 250 can be defined as arange of allowable effector outputs 220 for a given inceptor input 200.Maximum effector output, (δ_(O))_(MAX), 260 is also shown. Other formsfor model 150 may also be used. For example, the model 150 may includedata look-up tables or other formulas, equations, or other suitablemodeling techniques known in the art.

Returning to FIG. 1, the Model 150 is used to generate a desiredeffector output, (δ_(O))_(D), 160 from the inceptor input 200. Thedesired effector output 160 is compared to an actual effector output,(δ_(O))_(A), 170. Actual effector output 170 is measured by an effectorsensor 180. In various preferred embodiments, effector sensor 180measures effector 185 position and/or effector 185 rate.

Under normal operations, the inceptor input 200 and effector output 220values will lay within the tolerance band 250 of the Steady-StateInceptor Input/Effector Output Model 150, resulting in a distortionmetric value, E, 190 that will provide no additional feedback to theoperator 110 from the subject invention. However, degradation in thecontrol system 100 integrity and/or levels of inceptor 130 activityunder circumstances not envisioned during the design and developmentphase of the vehicle, which cause the inceptor input 200 and/or effectoroutput 220 values to exceed the tolerance band 250 of the Steady-StateInceptor Input/Effector Output Model 150, will result in feedback, tothe operator 110 from the subject invention.

Generally, the difference between the desired effector output 160 andthe actual effector output 170 is the value of the distortion metric, E,190, which, with the force feedback curve, sets the magnitude of thetactile feedback through the inceptor to the operator. The distortionmetric, E, 190 is generated from the comparison of the desired effectoroutput 160 to the actual effector output 170. A feedback force, F_(d),300 is determined from an evaluation of the distortion metric 190.Generally, the feedback force 300 is a function of the distortionmetric. In a preferred embodiment, the distortion metric 190 and thefeedback force 300 can be determined as follows:If δ_(I) K _(δO/δI)+Δδ_(O)>(δ_(O))_(A)>δ_(I) K _(δO/δI)−Δδ_(O), then E=0  (1)If δ_(I) K _(δO/δI)+Δδ_(O)≦(δ_(O))_(A)≦δ_(I) K _(δO/δI)−Δδ_(O), thendetermine E, where:E=[(δ_(I) K _(δO/δI)−Δδ_(O))−(δ_(O))_(A)]/(δ_(O))_(MAX), for(δ_(O))_(A)≦δ_(I) K _(δO/δI)−Δδ_(O), orE=[(δ_(O))_(A)−(δ_(I) K _(δO/δI)+Δδ_(O))]/(δ_(O))_(MAX), for(δ_(O))_(A)≦δ_(I) K _(δO/δI)+Δδ_(O), then   (2)F _(d) =f(E), where f(E) is a predetermined feedback force curve 330 forthe vehicle.   (3)

By using the distortion metric 190 as the input to the force feedbackcurve 330, the system 100 is an active and adaptive feedback controlsystem. The system 100 can adapt to changes in the electromechanicallinkages between the inceptor 130 and the effector 185. Furthermore, thesystem 100 actively compares desired effector output 160 to the actualeffector output 170, which, in other words, compares what should behappening in the system 100 to what is actually happening in the system100 and taking corrective measures when the two are sufficientlydifferent.

Feedback force 300 is used as an input to a feedback force generator 310which generates a LOCIS force 320 back to the inceptor 130. The LOCISforce 320 is felt by the operator 110 through the inceptor 130. Thefeedback force generator 310 can be of any type known in the art,including, but not limited to, the magnetically controllable devicesdiscussed above.

FIG. 3 shows inceptor/effector responses with and without a loss ofcontrol inhibitor system 100 according to the present invention. In theconditions shown, namely, a normal vehicle, a vehicle with a jammedeffector, a vehicle with a control limiting function, a vehicle with amisrigged effector, a vehicle with worsening wear, and a vehicle with arate limiting function, LOCIS force 320 is shown as a function ofinceptor input 200. Without the present invention, LOCIS force 320 isdirectly proportional to inceptor position. With the present invention,LOCIS force 320 varies with each of the conditions, yet remains the samefor a normally operating vehicle.

In various preferred embodiments, the vehicle having the presentinvention can be an aircraft, where the inceptor 130 is the aircraftyoke and or the rudder pedals and the effector 185 is any one orcombination of the control surfaces. In other various preferredembodiments, the vehicle having the present invention can be anautomobile, where the inceptor 130 is the steering wheel and/or thebrake pedal and the effectors 185 are the vehicle wheels and brakes.

While specific embodiments have been illustrated and described, numerousmodifications come to mind without significantly departing from thespirit of the invention and the scope of protection is limited by thescope of the accompanying claims.

1. A loss of control inhibitor system for a vehicle, said systemcomprising: an inceptor for receiving a control input from an operatorof said vehicle, an effector for effecting a control output in responseto said control input from said operator of said vehicle, an inceptorsensor, wherein said inceptor sensor measures a value of said controlinput, an effector sensor, wherein said effector sensor measures anactual effector output of said effector, means for modeling arelationship between said control input and said control output for apredetermined range of conditions, wherein said modeling means producesan expected effector output from said control input, means fordetermining a distortion metric, wherein said distortion metriccomprises a difference between said expected effector output and saidactual effector output, and means for providing a feedback force to saidinceptor, wherein said feedback force is a function of said distortionmetric.
 2. The loss of control inhibitor system for a vehicle accordingto claim 1, wherein said inceptor sensor comprises a positiontransducer.
 3. The loss of control inhibitor system for a vehicleaccording to claim 1, wherein said effector sensor comprises a positiontransducer.
 4. The loss of control inhibitor system for a vehicleaccording to claim 1, wherein said value of said control input comprisesan inceptor position.
 5. The loss of control inhibitor system for avehicle according to claim 1, wherein said value of said control inputcomprises an inceptor rate.
 6. The loss of control inhibitor system fora vehicle according to claim 1, wherein said actual effector outputcomprises an actual effector position.
 7. The loss of control inhibitorsystem for a vehicle according to claim 1, wherein said actual effecroroutput comprises an actual effector rate.
 8. The loss of controlinhibitor system for a vehicle according to claim 1, wherein saidvehicle is an airplane.
 9. The loss of control inhibitor system for avehicle according to claim 8, wherein said inceptor is a yoke.
 10. Theloss of control inhibitor system for a vehicle according to claim 8,wherein said inceptor is a rudder pedal.
 11. The loss of controlinhibitor system for a vehicle according to claim 1, wherein saidvehicle is an automobile.
 12. The loss of control inhibitor system for avehicle according to claim 11, wherein said inceptor is a steeringwheel.
 13. The loss of control inhibitor system for a vehicle accordingto claim 11, wherein said inceptor is a brake pedal.
 14. The loss ofcontrol inhibitor system for a vehicle according to claim 13, whereinsaid effector is a brake.
 15. A method of inhibiting loss of control ina vehicle, said method comprising the steps of: receiving a controlinput via an inceptor from an operator of said vehicle, effecting acontrol output via an effector in response to said control input fromsaid operator of said vehicle, measuring a value of said control input,measuring an actual effector output of said effector, modeling arelationship between said control input and said control output for apredetermined range of conditions, producing an expected effector outputfrom said control input using said relationship, determining adistortion metric, wherein said distortion metric comprises a differencebetween said expected effector output and said actual effector output,determining a feedback force as a function of said distortion metric,and providing a said feedback force to said inceptor.
 16. The method ofinhibiting loss of control in a vehicle according to claim 15, whereinmeasuring a value of said control input comprises measuring an inceptorposition.
 17. The method of inhibiting loss of control in a vehicleaccording to claim 15, wherein measuring a value of said control inputcomprises measuring an inceptor rate.
 18. The method of inhibiting lossof control in a vehicle according to claim 15, wherein measuring anactual effector output comprises measuring an effector position.
 19. Themethod of inhibiting loss of control in a vehicle according to claim 15,wherein measuring an actual effector output comprises measuring aneffector rate.